That has a lot of options, especially as you can copy a non-creature artifact like Spine of Ish Sah or Gilded Lotus
For example, some Pokmon have abilities that let you attach Energy from your discard pile or from your deck directly to them
We can quickly fill our graveyard with any of blues looting spells, like Ideas Unbound and Frantic Search, then make Rex unblockable with whites protection spells and blues unblockable cantrips
If it is tails, you get 30 damage HP
FromTheShire: Absolute worst case it's redundancy which is never a bad thing to have, but counters decks can easily be doing things on each turn to somewhat break the restriction and this has the upside of counting any permanents, not just creatures
(So yes, for those that like to dwell of the minutiae, technically permanents with landfall that change state do fall into the overall threshold category.) Let's look at another classic Magic card from days long ago: Is this a threshold card